There are not terms spelled out in the contract/lease? If not well then now you're up to a persons word and unfortunately that can change depending on the individual and circumstances. All my contracts have net 30 and 1%/mth for late payment. I have been sometime lenient with a couple customers but they also better have a good explanation and I do not let it happen more than once and not per customer, only the ones that are 'friends' in the business.
I say 30 days is about norm so if they haven't paid yet and should have, give them a call to find out what is going on and if the response you get isn't to your liking, follow-up with a register letter explaining this is standard practice. At least then you have something documented they owe monies to you.